Forty Days or 40 Days may refer to:
Christianity
Forty days in the desert, the Temptation of Christ
Books The Forty Days of Musa Dagh (), a 1933 novel by Franz Werfel
Music 40 Days, an album by the Wailin' Jennys, 2004 "40 Days", a song by Blessthefall from Awakening, 2011 "Forty Days", a 1959 song by Ronnie Hawkins and the cover of "Thirty Days" by Chuck Berry, 1955 "Forty Days and Forty Nights", a song by Muddy Waters, 1956 "Forty Days and Nights", a song by the Rankin Family, 1996 "40 Days", a song by Slowdive from Souvlaki, 1993 "40 Days", an instrumental song by Dave Brubeck, 1965 "Forty Days", a song by Streetlight Manifesto from Somewhere in the Between, 2007